The present invention relates to a power circuit for domestic electrical appliances having a remote control function, and more particularly to a power circuit which reduces a current consumed in the household electrical appliances during a waiting period of time.
As a conventional power circuit for household or domestic electrical appliances having a remote control function, there has been known a power circuit using means for converting an a.c. voltage into a d.c. voltage (hereinafter referred to as xe2x80x9cAC-DC converterxe2x80x9d) as shown in a circuit diagram of FIG. 3. That is, an output voltage of the AC-DC converter 101 permits a control circuit for remote control, in this example, a microcomputer and an infrared ray receiving circuit, 103 for producing an output signal 110 in response to an infrared signal 115 received from an external controller to be driven.
In the circuit of FIG. 3, in a domestic electrical appliance such as a television, power must be continuously applied to the infrared ray receiving circuit and the microcomputer because the electrical appliance receives a remote control signal even if an image reception turns off. This is called xe2x80x9cwaiting-time consumed powerxe2x80x9d. However, the efficiency of the AC-DC converter is low, and a power of about 1 W is consumed only for such a waiting-time consumed power. Under existing environmental issues, a demand has been made to reduce the consumed power at the waiting time as much as possible, which cannot be achieved by the existing circuit structure at all.
In order to solve the above problem, electricity is stored in electric charge storing means such as a secondary battery or an electric double layer capacitor so as to supply power to the microcomputer and the infrared ray receiving circuit without always operating the AC-DC converter. Before a voltage across the electric charge storing means becomes lower than a given value, specifically, the lowest operating voltage of the microcomputer and the infrared ray receiving circuit, the AC-DC converter is operated to charge the electric charge storing means whereas before the voltage rises to and the given voltage, specifically, the highest operating voltage of the microcomputer and the infrared ray receiving circuit, the AC-DC converter stops charging the electric charge storing means. With the above operation, the operating frequency of the AC-DC converter is reduced so that the power consumed by the AC-DC converter which is the worst in power efficiency is reduced, thereby making it possible to reduce the entire waiting-time consumed power.